In a dry etching, an end point is generally determined when an emission intensity of a plasma at a certain time falls by a predetermined degree from the emission intensity. Herein, it is desirable that a reference emission intensity at a certain time is not changed.
In recent years, there is proposed a nonvolatile semiconductor memory device having a three-dimensional structure in which memory cells are disposed in a stacked structure. In such a structure of the nonvolatile semiconductor device having the three-dimensional structure, an etching process is performed on a stacked body in which a plurality of different types of films are alternately stacked. The emission intensity of the plasma is undulated when the stacked body is subjected to the etching. Therefore, when an end point detection method generally used in the dry etching is employed, a variation occurs in an end point detection time.